The atmospheric mechanisms behind the storms of 1861-62 are unknown; however, the storms were likely the result of an intense atmospheric river, or a series of atmospheric rivers, striking the U.S. West Coast. With the right preconditions, just one intense atmospheric river hitting the Sierra Nevada mountain range east of Sacramento could bring devastation to the Central Valley of California. An independent panel wrote in October 2007 to California’s Department of Water Resources, “California’s Central Valley faces significant flood risks. Many experts feel that the Central Valley is the next big disaster waiting to happen. This fast-growing region in the country’s most populous state, the Central Valley encompasses the floodplains of two major rivers—the Sacramento and the San Joaquin—as well as additional rivers and tributaries that drain the Sierra Nevada. Expanding urban centers lie in floodplains where flooding could result in extensive loss of life and billions in damages.